Unpin sphinx in requirements.txt

[stevepiercy]

Sphinx is currently pinned to sphinx<9 as a temporary workaround to #2036.

Ultimately, I need to complete work on Plone Sphinx Theme v2.0.0 and release it to remove the dependency on Sphinx Book Theme.

[Shyam-Raghuwanshi]

Hi @stevepiercy we’ve implemented a temporary workaround for the original issue #2036. Could you please share your thoughts on what might be causing the underlying issue?

[stevepiercy]

@Shyam-Raghuwanshi see the issue description.

[Shyam-Raghuwanshi]

Hi @stevepiercy, I'd like to help with this issue. Could you share some guidance on:

What work remains to complete Plone Sphinx Theme v2.0.0?
Is there a development branch I can contribute to?
What specifically needs to be done to remove the Sphinx Book Theme dependency?
I'm happy to help with the development work if you can point me in the right direction

[stevepiercy]

@Shyam-Raghuwanshi thank you for your offer, but I need more free volunteer time, which I don't think you can provide. It's a very complex issue that requires deep familiarity with Sphinx, the themes we use and customize, and many more factors.